730

THE COLLIERY GUARDIAN.

October 2, 1914.

Mr. W. Maurice said that he supposed that most of
them accepted the general theory that the line of break
of the working face should be as nearly continuous as
possible, and more or less parallel to the face, and at a
suitable distance behind it. But the difficulty was that
in longwall work they had roads running more or less
at right angles to the working face, and at distances
apart of from 20 up to 60 yds. or more. These roads,
generally speaking, were supported by timber, and while
they were setting and removing timber systematically
at the face in order that the roof might break off pro-
perly at the back of the face, they were all the time
setting timber in the roads to hold up the roof and
prevent it from breaking. Consequently, it seemed to
him that there was an interruption to the proper break-
ing of the face owing to the fact that they had these
rigid supports at fixed intervals all the way along it.
Some years ago he was asked to report upon a system
of props in a Continental mine. In this case the sup-
ports were not tubular — or rather they were semi-
circular, or split tubes flanged on each side. They were
equal in height to three-fourths of the road in which
they were used,' and the two halves were clamped with
half-round clamps. A wooden block was driven into
the bottom end next the floor, then the tube was filled
to the extent of one-third of the way up with peat, the
next third with holing dirt, and the upper third was filled
in with a piece of old pit timber. There would be 18 in.
or 2 ft. of timber resting on the prop filled in the way
he had described. About two-thirds of the way down
the tube, at the point where the peat joined the holing
dirt, there was a slot, which ordinarily was covered by
a clamp. The roof gradually settled down until the
amount of timber at the top of the prop had disappeared
within it. When the pressure became so great that the
prop showed a tendency to bulge, the clamp over the
slot was removed, and men who took the place on the
Continent of the datallers in this country, and who were
furnished with a pick-pointed hammer, picked out some
of the holing dirt, and so relieved the prop from time
to time, until, as he had said, the top timber had dis-
appeared within the prop. The height was so calculated
that when that occurred it was necessary to re-rip the
road, a fresh piece of timber was inserted at the top,
and the whole process was repeated. He saw the
method in operation over several hundred yards of road,
and whereas formerly eight men were required to keep
that length in repair, the installation of the new system
made it necessary for only two men to keep walking
about to pick the dirt out of the slots whenever the indi-
cations of pressure showed that it was needful to do it.
The system appeared to him an attractive one, and he
was able to report upon it favourably, but he thought at
the time, and his opinion was unaltered, that it was
doubtful whether it would be practicable at a British
colliery. The application of the principle demanded a
point of view—a temperament, perhaps, he might say

The President observed that Mr. Fryar had pointed
out that the coal dust in the Nottingham area was not
so inflammable as in some other districts. It seemed
to him that it would be necessary to have an analysis
of each kind of coal dust before they could say what
amount of stone dust was necessary to make it safe.
The most varied proportions had been Suggested, but
they must remember that most of the experiments—if
not all—had been made with coal dust which came from
fiery seams, and which had been artificially reduced to
extreme fineness. What he was looking for was experi-
ments with coal dust taken* exactly as it was found in
the road. He remembered some years ago in a colliery
in the South Midland district an ignition of gas taking
place through a fall of roof in the main roadway, raising
a huge cloud of dust. In some districts that would have
been extremely dangerous, but in the case he had men-
tioned the dust was so inert that it had no effect what-
ever.

Mr. Binns said that there were a large number of

Fig. 1—General Arrangement of Pneumatic Coal-Transporting Plant tq Boilers. (section. 1

Belt Conveyor

Belt Conveyors



Fig. 2.—General Arrangement or Pneumatic Coal-Transporting Plant to Boilers (plan.)

A NEW METHOD FOR TRANSPORTING
SMALL COAL.*

By Edward Koenigs.

The application of the pneumatic principle to the
transporting of fine material is a matter which has been
in practice for several years, but it has been chiefly
limited to the transport of seeds, most especially com.
We may mention in this connection a very important
plant existing in Genoas harbour, which is considered
one of the finest of its kind. It is used for unloading
the corn from the hatches into large depots, and the
operation of unloading also includes the automatic
closing of the corn into sacks and the automatic
weighing of same.

Only lately has pneumatic transport been applied to
small coal, and the delay in its application is perhaps
due to some special difficulties which the transporting
of this material presents. The two chief difficulties
consist of the facts that small coal is not so uniform in
size as a certain quality of grain may be, and it usually
contains a certain quantity of moisture, which makes its
suction into the pneumatic pipes very difficult. Another
difficulty of secondary importance is the great quantity

I

Fig. 3.—Elevation of Plant at Paper Mills.





—which was not’natural to workmen in this country.
To put it in a popular way, it would be regarded as
rather “ fiddling ” work to go round and pick dirt out
of a hole, when an English workman would prefer to
go and bang away at something with a sledge-hammer,
even though he might accomplish less. The system
itself was sound, and if it failed it failed because the
people who had to work it did not take it the right way.
On the Continent the exploiters of pit props usually
ascertained what had been the timbering cost at a col-
liery, and then offered to supply their props for nothing
if they received half the saving effected by their use.
Whether that was sound finance or not he did not know,
but that was how it was worked there.

Mr. Binns thought that it would be useful to wait
for the report of the Commission which had gone out to
North America. They would then be able to learn
whether Canadian timber would help them, or whether,
as some of them thought, it was too dear.

The further discussion of the subject was then
adjourned to a future meeting.

Stone-dusting at Bentley Colliery.

A short discussion then took place on Mr. Robt.
Clive’s paper on “ Stone-dusting at Bentley Colliery :
Report to the Doncaster Coal Owners’ (Gob Fires)
Committee.”

physical problems to be considered in these explosions
of coal dust—not the least of which was the amount of
electricity generated by the friction of particles in the
air. The only way was to find out what would not
explode, and to make that the minimum.

The Reversal of Air Currents.

Mr. Clifford’s paper on “ Some Experiences in
Reversing the Main Air Currents in Coal Mines and
Mechanical Structures Involved ” was briefly discussed.

The President said that in America it was the practice
to reverse the air current almost at any time. The
reason was that they got their shafts partly frozen up,
and they had to reverse in order to send up the warm
air and set the shaft free.

Mr. R. Blunt (Swadlincote) said it would be interest-
ing to have careful measurements of the air current after
it had been reversed. The Act stipulated for an
efficient ” means of reversing the ventilation, but what
quantity had they to get when the current had been
reversed as compared with the quantity they usually had
going through? In other words, what was to be
regarded as “ efficient ”?

This concluded the meeting.

of dust which is created by the suction of small coal.
These difficulties have been dealt with in a long series
of experiments, the results being that, through several
modifications introduced in the machinery, they have been
largely overcome, and as a result of the improvements
introduced up to now, plants for the pneumatic trans-
port of small coal have lately been built on a large scale.

The plant represented in figs. 1 and 2 is actually in
use in a large industrial works in Austria, and dealing
with about 200 tons of coal in 24 hours. As may be
seen from the drawings, the whole apparatus for the
pneumatic transporting plant is situated in one building
marked a, which is placed over the railway line between
the boiler houses 1 and 2. The main apparatus for this
installation are the receiver b, the two dust filters c, Cj,
and a double cylinder air pump d, wfliich is placed in the
engine-house. From the cover of the receiver b are two
pipes e eT which lead to the filters c, cv To the cover
of these two filters are attached two pipes f,
connecting the filters with the air pump d. The lower
conical part of the receiver b is made airtight by means
of a rotating discharging arrangement, which is clearly
shown in fig. 4 ; and which, whilst allowing the outlet of
the coal, makes impossible the inlet of the air. A
similar discharging arrangement is attached to the
lower part of the filters for the automatic dis-
charging of the dust which is collected therein

* From the Proceedings of the South Wales Institute of
Engineers.